1. Field of the Invention
This invention relates to a mobile packet communications system, a mobile packet communications method, and a radio network controller that are adapted to provide a packet communications service to mobile stations.
2. Description of the Relevant Art
A typical mobile packet communications system employs, in view of the efficiency in use of frequency as well as a permissible delay in the packet communications, a method of time-multiplexing data of a plurality of users in a single radio channel. In this mobile packet communications system, which has as equipment to its radio base station or radio network controller a user data buffer provided every user for temporary storage of data of the user, the limit in amount of data that can be stored in the user data buffer does constitute a hardware-dependent limitation to the number of concurrently connectable users, that is, the number of concurrently settable packet calls (calls for packet communications).
In the typical mobile packet communications system, however, the user data buffer has a sufficient region secured for data storage thereto, which could admit packet calls as setup-requested from users until the user data buffer fills up. In such situation, it is regarded as a problem that increased transmission delay causing a degraded quality occurs.
For solution of this problem, in a known mobile packet communications system, the setup of packet call setup-requested from user is controlled not for admission up to a limit of hardware, but for admission in dependence on the condition of use of down-link transmission power.
An entire configuration of the mobile packet communications system is shown in FIG. 1. This mobile packet communications system is configured, as shown in FIG. 1, with mobile stations 10, radio base stations 20, radio network controllers 30, and an exchanger 40.
Each mobile station 10, connected by a radio connection to a radio base station 20, is configured with a radio communications terminal, such as a portable telephone terminal (with an IMT-2000 conforming portable telephone terminal inclusive), or a portable information terminal (PDA).
Each radio base station 20, connected by radio connections to mobile stations 10, is connected by a wired connection or radio connection to a radio network controller 30. Radio base station 20 is controlled by radio network controller 30, for radio communications with mobile stations 10 residing within a cell region under own control.
Each radio network controller 30 is connected to the exchanger 40 and to radio base stations 20, and controls the radio base stations 20 to control radio communications of mobile stations 10. Radio network controller 30 receives a “call admission request (setup request of packet call)” from a mobile station 10, as it is transmitted via a radio base station 20, and performs a decision of whether or not to admit packet call for the admission request, and upon a decision for admission of packet call, transfers to the exchanger 40 a request for the setup of packet call.
FIG. 2 diagrams simply part of configuration of radio network controller 30 associated with the above-noted control in the mobile packet communications system described. As shown in FIG. 2, radio network controller 30 is configured with a call processor 31, a call admission controller 32, and a memory 33.
The call processor 31, connected to the call admission controller 32, receives a call admission request from mobile station 10 and transfers the same to the call admission controller 32. Further, the call processor 31 answers the mobile station 10 of a result of a decision transmitted from the call admission controller 32 as to whether or not to admit packet call for the above-noted call admission request.
The call admission controller 32, connected to the call processor 31, decides whether or not to admit packet call for the call admission request transferred from the call processor 31, and transmits a result of the decision to the call processor 31. The call processor 31 is periodically reported from radio base station 20 of “down-link transmission power P” in current use at the radio base station 20. The call admission controller 32, holding a “prescribed threshold T”, performs a decision of whether or not to admit packet call for the call admission request transferred from the call processor 31, depending on a result of comparison of the “down-link transmission power P” and the “prescribed threshold T”.
The memory 33, connected to the call admission controller 32, stores therein information on currently set packet calls. The information encompasses, as shown in FIG. 2 for example, a “call ID” that is information for discrimination of a currently connected packet call, a “release timer” that indicates a residual time up to a release of the packet call, a “connected number of calls” that indicates the number of currently connected packet calls, etc.
The exchanger 40, connected to radio network controller 30, performs an exchange process relative to a setup request of packet call transferred from the radio network controller 30. The exchanger 40 is connected via a trunk network 100 to other exchangers.
FIG. 3 shows actions to be taken when a call admission request is transmitted from a mobile station 10 in the mobile packet communications system described.
As shown in FIG. 3, at a step S802, the call processor 31 of a radio network controller 30 receives a call admission request transmitted from the mobile station 10 via a radio base station 20. At a step S804, the call admission controller 32 of the radio network controller 30 receives the call admission request transferred from the call processor 31.
At a step S806, the call admission controller 32 compares a magnitude of “down-link transmission power P”, which is periodically reported from the radio base station 20 as in current use at the radio base station 20, with a “prescribed threshold T” under own control.
If the “down-link transmission power P” is smaller than the “prescribed threshold T”, the flow of control goes to a step S808, where the call admission controller 32 transmits to the call processor 31 a “call admission permission notice” notifying an admission of packet call to be effected for the above-noted call admission request, and stores in the memory 33 information on a call associated with the call admission request.
Unless the “down-link transmission power P” is smaller than the “prescribed threshold T”, the flow goes to a step S810, where the call admission controller 32 transmits to the call processor 31 a “call admission rejection notice” notifying no admission of packet call to be effected for the above-noted call admission request. The call processor 31 is responsible for the “call admission permission notice” or “call admission rejection notice” transmitted from the call admission controller 32 to execute a necessary process relative to the call admission request from the mobile station 10.
In the mobile packet communications system described, however, a controller for setting a circuit-switching-oriented call (voice call) is applied to the setup of packet call as well, with an occasional failure to exhibit an expected effect.
For example, for a radio base station 20 that has many mobile stations 10 performing radio communications in places relatively vicinal thereto and can do with a small amount of down-link transmission power P to be used there, the call admission controller 32 of an associated radio network controller 30 may admit setup admission of an excessive number of packet calls, with the result that an increased transmission delay causes a degraded quality, as a problem under the above-noted condition in the mobile packet communications system described.
In the case of a radio base station 20 has many mobile stations 10 performing radio communications in places relatively distant therefrom, the above-noted problem does not occur due to control depending on the down-link transmission power P. In such situation, however, a single radio channel may undergo a time division to be commonly employed by a plurality of users, leading to a failure to well utilize such an advantage of mobile packet communications that users are allowed to perform radio communications unless their data have temporal overlaps even when a great magnitude of down-link transmission power P is used at the radio base station 20. As a result, a problem that a reduced throughput over an entirety of the mobile packet communications system occurs.